Telephone-exchange system.



. v Patented Dec; 4, 1900-. E A. STROMBERG & w. M. DAVIS.

TELEPHONE EXCHANGE SYSTEM.

. (Application filegi June 28, 1900.) (N o M o d e I ALFRED STROMBERG AND WILLIAM M. DAVIS, OF CHICAGO, ILLINOIS,

ASSIGNORS TO THE STROMBERG-CARLSON TELEPHONE MANUFAC- TURING COMPANY, OF SAME PLACE.

TELEPHONE-EXCHANGE SYSTEM.

SPECIFICATION forming part of Letters Patent N 0. 662,988, dated December 4, 1900.

Application filed June 28, 1900. Serial No. 21,894. (No model.)

To 00 whont it may concern:

Be it known that we, ALFRED STROMBERG and WILLIAM M. DAVIS, citizens of the United States, residing at Chicago, in the county of Cook and State of Illinois, have invented a certain new and useful Improvement in Telephone-Exchange Systems, (Case No. 3,) of which the following is a full, clear, concise, and exact description, reference being had to the accompanying drawing, forming a part of this specification.

Our invention relates to telephone-exchange systems, and is particularly adapted for use in connection with those systems in which the telephone-lines extend from the central office to subscribers stations equipped with call-sending generators for operating signals at the exchange, although the invention is capable of other use, and has for its object the provision of an improved clearing-out annunoiator that will, after being operated, be automatically restored upon the manipulation of the operators apparatus.

In accordance with our invention we associate the magnet of a clearing-out annunciator with the cord-circuit in such a way that it may be traversed by current transmitted from the signaling-generator operated at a subscribers station that is connected with another through the agency of said cord-circuit.

The armature of the magnet when attracted serves to close a circuit including a battery or other source of current that serves to maintain the clearing-out signal, this second circuit including the separable contacts of a switch controlled by the operator, this switch when operated serving to open this latter circuit and restore the clearing-out indicator to its normal idle condition of use. In the preferred embodiment of our invention we profer to include the separable contacts of the operators listening-key in this second or subsidiary clearing-out-indicator circuit, so that the operatorin testing the line upon the manifestation of the clearing-out signal will at the same time open the subsidiary circuit and cause the restoration of the indicator.

We will explain our invention more particularly by reference to the accompanying drawing, illustrating the preferred embodiment thereof, in which a telephone-exchange system including two subscribers stations connected with the exchange is diagram matically indicated.

We have illustrated a well-known form of substation apparatus at each of the stations A and B, comprising a telephone switclrhook a, con nected with the limb b of each telephoneline, a magneto calling-generator c constituting the preferred source of signaling-current, a call-bell d, telephone-receiver e, and a transmitter f, in this instance a magneto-transmitter or a local battery transmitter, the switch-hook a serving to include either the telephone or the generator and bell in circuit, according to its position.

The limbs of the telephonelines b and g extend to the exchange and are there connected, respectively, with the short and long line-springs h and z', the longer line-spring being provided with a back contact it. Each line is provided with a line-indicator 1, whose helix is preferably bridged between the limbs 11 and g, the contacts 2' and It being included in series with said helix. The armature m is connected with limb g, and the contact at, which is adapted to be engaged by the armature when actuated, is connected with one terminal of a battery 0, the otherterminal of which is connected with the limb b. The battery 0 is thus normally in open circuit with the helix of each line-indicator, this circuit being normallybroken at the contacts m and n. The indicator proper is preferably in the form of an incandescent lamp 13, that is included in circuit with the battery 0 and the contacts m and it. When a calling subscriber signals the exchange, the magnet of his line-indicator is operated and circuit is closed through the lamp 1). The circuit through the lamp may be traced in detail from one pole of the batteryo or otherequivalent source of current to one limb b of the telephone-line, the helix of magnet Z, the back contact 70, line-spring 1}, engaging the same, the armature m, connected with the limb g of the telephone-line that extends to the linespring 2', the contact-anvil or, engaged by the actuated armature, the lamp 1), back to the remaining terminal of the battery 0. The operator in answering the call inserts the answering-plug q, and thereby separates contacts 71 and t to open the circuit through the indicator 19. She completes the connection by the insertion of the connecting-plug 7-.

So much of the apparatus as has been specifically described with reference to the d rawin'g we do not claim as our own invention.

The cord-circuit is provided with a clearing-out indicator, the helix of whose operating-magnet s is included in series with an impedance-coil t, and together with said impedance-coil in bridge between one terminal of the battery 0, connected with the limbs b of the telephone-lines, and the sleeve-strand of the cord-circuit adapted for connection with the line-springs 2', whereby the helix of the indicator is adapted to be operated by but,

current from the signaling-generator at a connected subscribers station. The helix of said magnet is also included in a normally open local circuit with the impedance-coil t, the battery 0, the armature u, the contact i), normally separated therefrom, the lamp 10, that constitutes the preferred form of clearing-out signal, a key-lever spring 00, and its normal contact 3 The contacts as, when moved against their alternate contacts, serve to include the operators telephone set in bridge of the telephone-circuit between subscribers stations. In the preferred practice the operator when a clearing-out signal is manifested bridges her telephone-set into the circuit to ascertain whether the subscribers have finished conversation. Thus after the signal to is operated upon a closing of the local circuit including the battery 0 the operator manipulates her listening-key to include her telephone in circuit and at the same time to separate the contacts as and y, whereupon the local circuit, including the helix of the magnet s, is broken, the said magnet dee'nergized, and the clearing-out signal to restored.

We do not wish to be limited to the precise apparatus herein shown and particularly described nor to the location of the signaling-generators at the subscribers stations;

Having thus described our invention, we claim as new and desire to secure by Letters Patent- 1. In a telephone-exch ange system,the combination with subscribers lines extending from substations to an exchange, of a source of callingcurrent at each subscribers station, a clearing-out indicator at the exchange, associated with united telephone-lines, a battery includedin a normally open circuit with the helix of the clearing-out-indicator magnet, the armature of said magnet serving to close circuit through the battery and helix when actuated through the agency of the source of current at a subscribers station, and an operators switching appliance having normally closed separable contacts also included in circuit with the said battery and helix, the said contacts of the operators switching appliance serving, when separated,

to open the circuit previously closed by the armature of the clearing-out-indicator magnet to cause a restoration of the clearing-out indicator, substantially as described.

2. Inatelephone-exchange system,the combination with subscribers telephone-lines ex- I tending from substations to an exchange and there united in a telephonic circuit,of a source of calling-current at each substation, a clearing-out indicator at the exchange adapted to be operated by current from a substation, a battery, the magnet of the clearing-out indicator serving when actuated to include said battery in circuit with its helix to maintain said clearing-out indicatorin an actuated condition, and an operators listening-key adapted to exclude the battery from circuit with the clearing-out-indicator magnet, whereby the clearing-out indicator is restored,s ubstantially as described.

3. Inatelephone-exchangesystem,thecombination with subscribers lines extending from substations to an exchange, of a source of calling-cu rrent at each subscribers station a clearing-out indicator at the exchange, as-

sociated with united telephone-lines, a battery included in a normally open circuit with the helix of the clearing-out-indicator magnet, the armature of said magnet serving to close circuit through the battery and helix when actuated through the agency of the source of current at a subscribers station, and an operators listening-key having normally closed separable contacts also included in circuit with the said battery and helix, the said contacts of the operators listening-key serving, 5 when separated, to open the circuit previously closed by the armature of the clearingout-indicator magnet to cause a restoration of the clearing-out indicator, substantially as described.

4:. In a telephone-exchange system,the combination with telephone-lines extending from substations to an exchange and there united in a telephonic circuit, of a source of callingcurrent at each substation, a line-indicator for each line, a clearing-out indicator at the exchange adapted to be operated by current transmitted over the telephone-line from a substation, a battery, means whereby the magnet of the clearing-out indicator may include its helix in circuit with saidbattery when said magnet is operated to maintain the clearing-out indicator in an actuated con,- dition, and an operators switching appliance adapted to exclude the said battery from circuit with the clearing-out-indicator magnet, substantially as described.

v5. In a telephone-exchange system,the combination with subscribers lines extending from substations to an exchange, of a source of calling-current at each subscribers station, a line-indicator associated with each line, a clearing-out indicator at the exchange, associated with united telephone-lines, a battery included in a normally open circuit with the helix of the clearing-out-indicator magnet,

the armature of said magnet serving to close circuit through the battery and helix when actuated through the agency of the source of current at a subscribers station, and an operators switching appliance having normally closed separable contacts also included in circuit with the said battery and helix, the said contacts of the operators switching appliance serving, when separated, to open the circuit previously closed by the armature of the clearing-ont-indicator magnet to cause a restoration of the clearing-outindicator,substantially as described.

6. In a telephone-exchange system ,the combination with telephone-lines extending from substations to an exchange and there united in a telephonic circuit, of a source of callingcurrent at each substation, a line-indicator for each line, a clearing-out indicator at the exchange adapted to be operated by current transmitted over the telephone-line from a substation, a battery, means whereby the magnet of the clearing-out indicator may include its helix in circuit with said battery when said magnet is operated to maintain the clearing-out indicator in an actuated condition, and an operators listening-key adapted to exclude the battery from circuit with the magnet of the clearing-out indicator,substantially as described.

7. In a telephone-exchange system,the combinaiion with subscribers lines extending from substations to an exchange, of a source of calling-current at each subscribers station, a line-indicator associated with each line, a clearing-out indicator at the exchange, associated with united telephone lines, a battery included in a normally open circuit with the helix of the clearing-out-indicatormagnet, the armature of said magnet serving to close circuit through the battery and helix when actuated through the agency of the source of current at a subscribers station, and an operators listening-key having normally closed separable contacts also included in circuit with the said battery and helix, the said contacts of the operators listening-key serving, when separated,to open the circuit previously closed by the armature of the clearing-ont-indicator magnet to cause a restoration of the clearing-out indicator, substantially as described.

8. In a telephone-exchange system,the combin ation with subscribers telephone-lines extending from substations to an exchange and there united in telephonic circuit, of a clearing-out indicator at the exchange, a battery, means controlled by the magnet of the clearing-out indicator for including the helix of said magnet in circuit with said battery to maintain the clearing-out indicator in its actuated condition, and an operators listeningkey adapted to exclude the battery from circnit with the helix of said magnet to restore the clearing-outindicator,substantially as described.

9. In a telephone-exchange system,the combination with subscribers telephone-lines extending from substations to an exchange and there united in telephonic circuit, of a clearing-out indicator at the exchange, abattery, means controlled by the magnet of the clearing-out indicator for including the helix of said magnet in circuit with said battery to maintain the clearing-out indicator in its actuated condition, and an operators switching appliance adapted to exclude the said battery from circuit with the helix of the said magnet, substantially as described.

10. In a telephone-exchange system, the combination with a subscribers telephoneline extending from a substation to an exchange, of an indicator at the exchange, a battery, means controlled by the magnet of said indicator for including the helix of said magnet in circuit with said battery to maintain the said indicator in its actuated condition, and an operators listening-key adapted to exclude the battery from circuit with the helix of said magnet to restore said indicator, substantially as described.

11. In a telephone-exchange system, the combination with subscribers telephone-lines extending from substations to an exchange and there united in a telephonic circuit, of a source of calling-current, a clearing-out indicator at the exchange having an operatinghelix and adapted to be operated at a substation, an operators listening-key at the exchange, and means whereby the said listening-key may deenergize said helix to restore the clearing-out indicator after actuation, substantially as described.

12. In a telephone-exchange system, the combination with a subscribers telephoneline extending from a substation to an exchange, of a source of calling-current, an indicator at the exchange having an operatinghelix and adapted to be operated from a substation, an operators listening-key at the exchange, and means whereby the said listening-key may denergize said helix to restore the indicator after actuation, substantially as described.

13. In a telephone-exchange system, the combination with subscribers telephone-lines extending from substations to an exchange and there united in a telephonic circuit, of a source of calling-current, a clearing-out indicator at the exchange having an operatinghelix and adapted to be operated at a substation, an operators switching appliance at the exchange, and means whereby the said switching appliance may deenergize said helix to restore the clearing-out indicator after actuation, substantially as described?- In witness whereof we hereunto subscribe our names this 18th day of June, A. D. 1900.

ALFRED STROMBERG. WILLIAM M. DAVIS.

Witnesses:

GEORGE L. CRAGG, HARVEY L. HANSON.

IIO 

